Conventional projection systems are used to project images, such as from an LCD projector, or High Definition Television (“HDTV”), onto a large screen. Some conventional projection devices utilize the recently developed digital micromirror device (or “DMD”, which is a trade name of Texas Instruments). The DMD is a two-dimensional array of a number of pixels (e.g., 1024×768 pixels) each having a micromirror, which corresponds to the pixels of a video display. A DMD control unit controls the tilt of each mirror individually through the effect of an electrostatic field caused by a memory unit arranged for each pixel, respectively. The DMD control unit varies the angle of reflection of a reflected light ray thereby causing an on/off state. Thus, an image shown on a corresponding video display can be magnified and projected onto the large screen.
Many conventional projection systems utilize a linear optical path for the illumination beam, which entails straightforward alignment. However, the physical length required to provide adequate imaging necessarily creates a need for a large housing volume. Another conventional projection system optical layout is shown in FIG. 10 of U.S. Pat. No. 6,129,437. This type of linear layout may provide acceptable optical throughput, but is limited in that significant housing space is required, especially in terms of physical height.
Thus, there is a need to make compact, lightweight, and high efficiency (e.g., high throughput) optical systems for use in electronic projection systems. Typically, in the above mentioned conventional optical projection systems, optical throughput is sacrificed in order to achieve the necessary system packaging goals.